I find 1 frame links in SF4 are hard depending on the normal youre linking off of. Elenas c.lk, c.lp is a 1 framer but I dont have much trouble hitting it consistently because the timing is very quick, almost like linking her jabs. Her 1 framer off her overhead is much harder to link though and it's why you dont see many Elenas go for it unless they got that select plink mod. Same goes with other jab 1 framers where the link is off of a normal that has lots of recovery or it's off a normal that can normally be chained. Getting that timing is much harder than something that recovers very quick and can only be linked.